A sequence of fossil forms that represent the succession of species in the evolution of a particular lineage. Often there are gaps in the fossil record, and phyletic series are incomplete. However, in some cases the fossil record is good, and a more complete phyletic series can be constructed. For example, most of the intermediate forms between the modern horse (Equus) and its dog-sized ancestor, Hyracotherium (Eohippus) of the Eocene epoch, have been charted.